The Effect of Reducing the Mixing Temperature on Fatigue Life of Asphalt Mixture

The cracks resulted from fatigue are one of the main types of failures in flexible pavements. The bitumen aging is one of the major factors of creating fatigue cracks. The bitumen used in asphalt mixture is exposed to hardening and aging during making the mixture as well as on the pavement. The aging mainly occurs due to bitumen oxidation with the oxygen existing in the air. This process in high temperature such as the mixing temperature of asphalt occurs more quickly when the bitumen covers the surface of aggregates with a thin film. The mixture of bitumen with aggregates in mixing temperature of asphalts can be considered as a stage in which the most sever oxidation and hardening of bitumen during production and making asphalt occurs. Therefore, the mixing temperature of aggregates and bitumen in asphalt factory is one of the most important factors of aging and the resulted fatigue of asphalt mixture. This is the reason why warm mix asphalts were used for reducing the mixing and compacting temperature.
The objective of the present research paper is studying the influence of reducing mixing temperature on fatigue life of the asphalt mixture. In this study, the asphalt mixture has been made in three temperatures of 100, 120 and 145 ºC in order to study the influence of mixing temperature. Sasobit and Asphamin have been used for reducing the mixing temperature. The results of testing show that the fatigue life of warm mix asphalt is higher than hot mix asphalt.The samples produced in 120 ºC have a higher fatigue life without any consideration to the type of additives and the samples containing Sasobit have a fatigue life higher than the samples with Asphamin.